border-1px($color)
    position: relative;
    &:after
        display block
        position absolute
        left 0
        bottom 0
        width 100%
        border-top 1px solid $color;
        content: '';

border-none()
    &:after
        display none

bg-image($url)
    background-image: url($url+"@2x.png");
    @media (-webkit-min-device-pixel-ratio: 3), (min-device-pixel-ratio: 3)
        background-image: url($url + '@3x.png');
        

